WO2012026442A1 - Method for hot-stamping galvanized steel sheet - Google Patents

Method for hot-stamping galvanized steel sheet Download PDF

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Publication number
WO2012026442A1
WO2012026442A1 PCT/JP2011/068911 JP2011068911W WO2012026442A1 WO 2012026442 A1 WO2012026442 A1 WO 2012026442A1 JP 2011068911 W JP2011068911 W JP 2011068911W WO 2012026442 A1 WO2012026442 A1 WO 2012026442A1
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WIPO (PCT)
Prior art keywords
galvanized steel
steel sheet
emissivity
alloying reaction
cooling
Prior art date
Application number
PCT/JP2011/068911
Other languages
French (fr)
Japanese (ja)
Inventor
好史 小林
泰則 伊藤
一之 河野
隆 八重倉
Original Assignee
新日本製鐵株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
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Application filed by 新日本製鐵株式会社 filed Critical 新日本製鐵株式会社
Priority to CN201180040668.3A priority Critical patent/CN103069041B/en
Priority to JP2012504951A priority patent/JP5015356B2/en
Priority to KR1020137003845A priority patent/KR101374472B1/en
Priority to CA2807332A priority patent/CA2807332C/en
Priority to EP11819905.8A priority patent/EP2599889B1/en
Priority to US13/812,408 priority patent/US8926770B2/en
Publication of WO2012026442A1 publication Critical patent/WO2012026442A1/en

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
    • B21D22/02—Stamping using rigid devices or tools
    • B21D22/022—Stamping using rigid devices or tools by heating the blank or stamping associated with heat treatment
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/62—Quenching devices
    • C21D1/673—Quenching devices for die quenching
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/06—Zinc or cadmium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/26—After-treatment
    • C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/26—After-treatment
    • C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
    • C23C2/29—Cooling or quenching
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
    • C23C2/36—Elongated material
    • C23C2/40—Plates; Strips
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/48—After-treatment of electroplated surfaces
    • C25D5/50—After-treatment of electroplated surfaces by heat-treatment
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/0003—Radiation pyrometry, e.g. infrared or optical thermometry for sensing the radiant heat transfer of samples, e.g. emittance meter
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/10—Radiation pyrometry, e.g. infrared or optical thermometry using electric radiation detectors
    • G01J5/12—Radiation pyrometry, e.g. infrared or optical thermometry using electric radiation detectors using thermoelectric elements, e.g. thermocouples

Definitions

  • the present invention relates to a hot stamping method for galvanized steel sheets such as hot dip galvanized steel sheets and electrogalvanized steel sheets.
  • Hot stamping is a forming method in which a steel sheet heated to a high temperature of Ac3 or higher is pressed with a mold and quenched by quenching inside the mold. According to the hot stamp, strength can be increased and shape stability can be ensured.
  • the heating of the steel plate in the previous stage of the hot stamp is often performed by furnace heating, near infrared heating, far infrared heating, induction heating, direct current heating, or the like.
  • the hot stamping material is a galvanized steel sheet
  • the galvanized steel sheet is heated to a temperature not lower than the Ac3 point and lower than the boiling point of zinc, and practically not higher than 900 ° C. in the heating step.
  • the zinc plating becomes a molten state, and the liquid phase diffusion of iron to the molten zinc proceeds.
  • the phase produced by this alloying is a ⁇ phase.
  • the timing of pressing is important for the following reasons. If the galvanized steel sheet is pressed before or immediately after the start of the alloying reaction, grain boundary embrittlement cracking of the steel occurs due to unalloyed molten zinc, and the product is not produced. Even if grain boundary embrittlement cracking does not occur in the steel, the molten zinc adheres to the inner surface of the mold, so that the mold must be frequently maintained. In addition, the amount of galvanizing on the surface of the product is insufficient, which leads to a decrease in corrosion resistance, leading to problems in the performance of the parts. For this reason, in the hot stamping of a galvanized steel sheet, it is desirable to perform pressing after finishing the alloying reaction in the intermediate cooling step.
  • the heating process and the intermediate cooling process should be properly managed and pressing be started at an appropriate timing. Is not easy. That is, conventionally, management based on the heating time, the heating temperature, the intermediate cooling time, and the temperature at which the press is started is empirically performed, but it is difficult to accurately determine the end of the alloying reaction.
  • Patent Document 1 discloses a method in which a galvanized steel sheet is heated to 800 ° C. to 950 ° C. in a heating furnace, then rapidly cooled to 500 ° C. to 730 ° C. with a quenching equipment, and then pressed.
  • this method is a special technique aiming at improving corrosion resistance and fatigue resistance, and also requires a quenching equipment, and cannot be applied to a general hot stamping of a galvanized steel sheet.
  • Patent Document 2 describes a method of observing the progress of the Fe—Zn alloy reaction during the production of the alloy Zn-plated steel sheet based on the spectral emissivity.
  • the temperature range in which observation is performed by the method described in Patent Document 2 is significantly lower than the temperature at which pressing is performed in a hot stamp. For this reason, the state of the surface of the galvanized steel sheet in the hot stamp intermediate cooling process cannot be detected by the method described in Patent Document 2.
  • An object of the present invention is to provide a hot stamping method for a galvanized steel sheet, which can be pressed and quenched after the molten zinc is surely lost.
  • the inventors measured the change in the emissivity of the surface of the galvanized steel sheet with an emissivity measuring device having a predetermined observation wavelength within a predetermined temperature range during cooling after heating, and based on the change in emissivity. It has been found that the start and end of the alloying reaction, that is, the disappearance of molten zinc can be detected.
  • the inventors corresponded to the following aspects of the invention.
  • an off-line test apparatus for hot stamping comprising the steps of heating the galvanized steel sheet and cooling the galvanized steel sheet.
  • the emissivity measuring device according to any one of (5) to (5) is installed and the measurement by the emissivity measuring device is executed, and from the start of cooling to the end of the alloying reaction is detected based on the change in the emissivity.
  • the alloying reaction end time is investigated, the control means stores the alloying reaction end time, and the control means determines that the alloying reaction end time has been reached accordingly.
  • a hot stamping method for a galvanized steel sheet, wherein hot stamping for starting the pressing and quenching is performed after the detection.
  • the step of heating the galvanized steel sheet and the step of cooling the galvanized steel sheet in the hot press method according to any one of (1) to (5) are performed. Further, in the step of cooling the galvanized steel sheet, the measurement by the emissivity measuring device is executed, and the alloying reaction end time from the start of cooling to the end of the alloying reaction is detected based on the change in the emissivity.
  • the alloying reaction end time is stored in the control means of the facility that performs the actual hot stamping,
  • the step of cooling the second galvanized steel sheet at substantially the same rate as when cooling the galvanized steel sheet
  • a step of pressing and quenching the second galvanized steel sheet Have In the step of cooling the second galvanized steel sheet, the elapsed time from the start of cooling is measured, A hot stamping method for a galvanized steel sheet, wherein the pressing and quenching are started after the control means detects that the elapsed time has reached the alloying reaction end time.
  • the end of the alloying reaction can be reliably grasped regardless of the type, basis weight, plate thickness, size, etc. of the galvanized steel plate. Therefore, pressing and quenching can be performed after the molten zinc is surely lost.
  • FIG. 1 is a block diagram showing equipment suitable for carrying out a hot stamping method for galvanized steel sheets according to embodiments (1) to (5) of the present invention.
  • FIG. 2 is a graph showing a change in temperature measured by a thermocouple and a change in temperature calculated by temperature conversion of emissivity.
  • FIG. 3 is a graph showing temperature-measured values by a thermocouple and emissivity temperature-converted display values by an emissivity measuring device using various observation wavelengths.
  • FIG. 4 is a graph in which the vertical axis is replaced with the rate of change of emissivity when the observation wavelength in the graph of FIG. 3 is 8 ⁇ m to 14 ⁇ m.
  • FIG. 5 is a block diagram showing equipment suitable for carrying out the hot stamping method for a galvanized steel sheet according to the embodiment (6) of the present invention.
  • FIG. 1 is a block diagram showing equipment suitable for carrying out a hot stamping method for a galvanized steel sheet according to an embodiment of the present invention.
  • the equipment includes a heating device 1 for heating the galvanized steel sheet W to a predetermined temperature, an intermediate cooling unit 3 for cooling the galvanized steel plate W taken out from the heating device 1 by cooling, and an intermediate cooling unit 3.
  • a press hardening apparatus 2 for pressing and quenching the cooled galvanized steel sheet W is provided.
  • an emissivity measuring device 4 for measuring the emissivity of the surface of the galvanized steel sheet W in the intermediate cooling unit 3 is provided.
  • the galvanized steel sheet W may be either a hot dip galvanized steel sheet or an electrogalvanized steel sheet.
  • the weight per unit area of hot-dip galvanized steel sheet is 50 g / m 2 the galvannealed steel sheet 60 g / m 2 or more, the electro-galvanized steel sheet 50 g / m 2 or more, the alloying galvanized steel sheet is required 60 g / m 2 or more.
  • the heating device 1 before the hot stamp various devices such as energization heating, a heating furnace, near infrared heating, far infrared heating, and induction heating can be employed.
  • an electric heating device When hot stamping automotive parts, it is preferable to use an electric heating device. This is because the current heating device is compact, and according to the current heating, a high heating rate can be obtained, so that the productivity can be improved, the heating temperature is easily controlled, and the galvanized steel sheet is heated uniformly. Because it can be done.
  • the maximum heating temperature in the heating device 1 is not less than Ac3 and less than the boiling point of zinc, and is practically in the range of 800 ° C to 900 ° C.
  • the heating rate of the galvanized steel sheet W is practically 10 ° C./second or more and 200 ° C./second or less, and is preferably in the range of 20 ° C./second to 200 ° C./second from the viewpoint of improving productivity.
  • the alloying reaction of iron and zinc proceeds by liquid phase diffusion of iron into molten zinc.
  • the temperature change of the hot-dip galvanized steel sheet when heating is performed in the heating device 1 and then cooling is performed in the intermediate cooling unit 3 will be described.
  • the temperature of the hot-dip galvanized steel sheet is measured by a thermocouple, and is calculated by converting the emissivity measured by the emissivity measuring device into a temperature.
  • the temperature measured by the thermocouple is referred to as the “temperature measurement value by the thermocouple”, and the value calculated by the temperature conversion of the emissivity measured by the emissivity measuring instrument is referred to as the “emissivity temperature conversion display value”.
  • the temperature converted display value of the emissivity is substantially equivalent to the emissivity value and its change.
  • FIG. 2 the temperature measurement value by a thermocouple and the temperature conversion display value of emissivity are shown. The solid line in Fig.
  • the heating rate in the heating device 1 is preferably in the range of 20 ° C./second to 200 ° C./second, which is relatively fast, from the viewpoint of improving productivity.
  • finish of alloying reaction shall be below the boiling point of zinc of a plating layer, and more than the ferrite transformation temperature of a steel plate.
  • the temperature range for grasping the end of the alloying reaction is set to be less than the boiling point of zinc in the plating layer because heating to a temperature higher than the boiling point causes the zinc to evaporate from the steel sheet surface and disappear, resulting in no longer a galvanized steel sheet. is there.
  • the reason why the temperature range is set to be equal to or higher than the ferrite transformation temperature of the steel sheet is to obtain a martensite structure stably by quenching in the press quenching apparatus 2.
  • heating is performed to about 880 ° C., which is a temperature below the boiling point of zinc, and the end temperature of the alloying reaction in the subsequent intermediate cooling step is about 700 ° C., while the ferrite transformation is about 650 ° C. Waking up at °C.
  • the boiling point of zinc varies slightly depending on the amount of other metal elements contained in the plating layer in the hot dip galvanized steel sheet, alloyed hot dip galvanized steel sheet, electrogalvanized steel sheet, and alloyed electrogalvanized steel sheet, but about 908 ° C It is.
  • the ferrite transformation temperature is in the range of 0.18 mass% to 0.25 mass% when the C amount of the steel sheet is suitable for hot stamping, and other chemical components of the steel sheet, the heating rate and the heating temperature in the heating apparatus 1, etc. However, it is about 650 ° C.
  • the temperature measurement of a galvanized steel sheet is generally performed using a thermocouple or a radiation thermometer. However, in the temperature measurement using a radiation thermometer, the difference is about 20 ° C. compared to the case where a thermocouple is used. May occur.
  • the inventor of the present application focused on the observation wavelength of the emissivity measuring device and the change in the temperature converted display value of the emissivity at that wavelength.
  • the galvanized steel sheet W heated to, for example, 800 ° C. to 900 ° C. in the heating device 1 is taken out to the intermediate cooling unit 3, and the emissivity of the surface of the galvanized steel sheet W heated in the heating device 1 is determined.
  • the measurement is performed with the emissivity measuring instrument 4 having a long wavelength of 1.4 ⁇ m or more, more preferably the emissivity measuring instrument 4 having an observation wavelength of 8 ⁇ m to 40 ⁇ m.
  • the surface state of the galvanized steel sheet W changes from liquid to solid, and the physical properties change. And the amount of infrared rays changes accompanying these changes.
  • the start and end of the alloying reaction are detected by continuously detecting such a change in the amount of infrared rays at the aforementioned long wavelength observation wavelength as a change in emissivity or a temperature-converted display value of emissivity. It is intended to grasp the disappearance of molten zinc.
  • thermopile For the emissivity measuring instrument 4 used in the present embodiment, a measuring element that is an InGaAs element or a thermopile is suitable, and a thermopile that can capture a large change in emissivity is particularly preferable.
  • the measuring element is a thermopile
  • the upper limit of the observation wavelength is practically 40 ⁇ m.
  • a thermopile is a converter in which a plurality of thermocouples are connected in series or in parallel, and is a converter having a function of converting heat energy into electric energy, and is also referred to as thermoelectric estimation.
  • a long wavelength emissivity measuring instrument 4 with an observation wavelength of 1.4 ⁇ m or more is used.
  • FIG. 3 the temperature conversion value by the emissivity by the emissivity measuring device using the temperature measurement value by a thermocouple and various observation wavelengths is shown.
  • the broken line in FIG. 3 shows the change in the temperature-converted display value of the emissivity from the start of heating when using a short-wavelength emissometer with an observation wavelength of 0.8 ⁇ m to 1.1 ⁇ m.
  • FIG. 4 shows a graph in which the vertical axis is replaced with the rate of change of emissivity when the observation wavelength in the graph of FIG. 3 is 8 ⁇ m to 14 ⁇ m.
  • the rate of change of emissivity (solid line) is substantially constant up to the starting point of the alloying reaction, increases at the starting point of the alloying reaction, decreases thereafter, and ends the alloying reaction. From the point it becomes almost constant again. That is, the rate of change of emissivity also varies greatly at the start and end points of the alloying reaction.
  • alloying becomes clearer.
  • the end point of the reaction can be determined. This determination can be grasped more clearly by differentiating the value obtained by smoothing the measured emissivity value by moving average processing or the like.
  • the point at which the negative value changes to the positive value is the alloying start point, and the point after which the positive value changes to the negative value is the alloying end point, it becomes clearer. The end point of the alloying reaction can be determined.
  • the moving average process is a technique for smoothing time-series data.
  • a simple moving average process may be performed.
  • the simple moving average process is a process for obtaining a simple average value that does not weight the latest n data from the latest data. When time advances and the latest data is measured, the latest data is added and n average values are obtained again except for the oldest data. In the simple moving average process, this is repeated thereafter.
  • the simple moving average processing is performed. At this time, data from the emissivity measuring device is sampled every 0.1 second, and the number of data of the moving average processing is 10.
  • a moving average process other than the simple moving average process may be used.
  • the galvanized steel sheet W is fed into the press hardening apparatus 2 and the press and quenching are started while the temperature is equal to or higher than the ferrite transformation temperature. That is, the completion of the alloying reaction is grasped, and after the molten zinc is surely lost, pressing and quenching are started.
  • the press and quenching can be started after the alloying reaction is completed regardless of the plating type, basis weight, plate thickness, size, etc. of the galvanized steel sheet W. Therefore, grain boundary embrittlement cracking of steel due to unalloyed molten zinc can be prevented. Moreover, the adhesion of the molten zinc to the inner surface of the mold of the press quenching apparatus 2 and the deterioration of the corrosion resistance due to the insufficient amount of galvanizing can be prevented.
  • the rate at which the rate of change in emissivity changes from a negative value to a positive value is determined as the starting point of the alloying reaction, and the point after which the rate of change from the positive value to the negative value is determined as the end point of the alloying reaction, it is more appropriate. Judgment is possible.
  • the measurement value of the emissivity measuring device 4 may be input to the calculation control device 5, and the calculation control device 5 may control the operation of the press hardening device 2.
  • the emissivity measuring instrument 4 when the emissivity measuring instrument 4 cannot be installed in equipment for performing hot stamping in terms of equipment, space or cost, for example, the emissivity measuring instrument 4 is attached to an off-line test apparatus, and this off-line test apparatus is installed. Then, the alloying reaction end time is investigated in the same manner as described above, and the alloying reaction end time is stored in the arithmetic control unit 5 of the facility that performs the actual hot stamping as shown in FIG. The elapsed time from the start of cooling is measured, and after the arithmetic and control unit 5 detects that the elapsed time has reached the alloying reaction end time, pressing and quenching may be started.
  • the heating temperature and the cooling rate after heating in the off-line test apparatus are the same as those in the facility that performs the actual hot stamping.
  • the desired temperature can be obtained even if there is some variation.
  • An effect is obtained.
  • the heating temperature in the actual equipment is kept within the range of ⁇ 10 ° C of the heating temperature in the offline test apparatus, and the cooling rate in the actual equipment is in the range of ⁇ 2 ° C / second of the cooling speed in the offline test apparatus. If it fits in, the desired effect can be acquired.
  • the present invention can be used, for example, in related industries of galvanized steel sheets used for vehicle bodies and the like.

Abstract

A galvanized steel sheet (W) is cooled, during which a surface of the galvanized steel sheet (W) is examined for change in emissivity in the range of temperatures which are lower than the boiling point of the zinc but not lower than the ferrite transformation temperature by means of an emissivity sensor (4) for wavelengths of 1.4 µm and longer. Pressing and quenching in a pressing/quenching device (2) are started after completion of the alloying reaction is detected on the basis of a change in emissivity. The emissivity sensor (4) preferably is a device in which the sensing element is an InGaAs element or a thermopile.

Description

亜鉛めっき鋼板のホットスタンプ方法Hot stamping method for galvanized steel sheet
　本発明は、溶融亜鉛めっき鋼板及び電気亜鉛めっき鋼板などの亜鉛めっき鋼板のホットスタンプ方法に関する。 The present invention relates to a hot stamping method for galvanized steel sheets such as hot dip galvanized steel sheets and electrogalvanized steel sheets.
　ホットスタンプは、Ａｃ３点以上の高温に加熱された鋼板を金型でプレスするとともに金型の内部で急冷することにより焼入れする成形方法である。ホットスタンプによれば、強度を高めるとともに、形状安定性を確保することができる。ホットスタンプの前段における鋼板の加熱は、炉加熱、近赤外線加熱、遠赤外線加熱、誘導加熱、直接通電加熱などにより行われることが多い。 Hot stamping is a forming method in which a steel sheet heated to a high temperature of Ac3 or higher is pressed with a mold and quenched by quenching inside the mold. According to the hot stamp, strength can be increased and shape stability can be ensured. The heating of the steel plate in the previous stage of the hot stamp is often performed by furnace heating, near infrared heating, far infrared heating, induction heating, direct current heating, or the like.
　このホットスタンプの素材が亜鉛めっき鋼板である場合には、加熱工程において亜鉛めっき鋼板はＡｃ３点以上、かつ亜鉛の沸点未満の温度、実用上は９００℃以下の温度に加熱される。この温度域まで加熱を行うと亜鉛めっきは溶融状態となって、溶融亜鉛への鉄の液相拡散が進行する。このため、加熱の終了からプレスの開始までの中間冷却工程で、溶融亜鉛中の鉄濃度が１５％～３０％となり、鋼板の温度が７８２℃を下回ると、亜鉛－鉄の合金化が進行する。この合金化により生成する相はΓ相である。 When the hot stamping material is a galvanized steel sheet, the galvanized steel sheet is heated to a temperature not lower than the Ac3 point and lower than the boiling point of zinc, and practically not higher than 900 ° C. in the heating step. When heating is performed up to this temperature range, the zinc plating becomes a molten state, and the liquid phase diffusion of iron to the molten zinc proceeds. For this reason, in the intermediate cooling process from the end of heating to the start of pressing, when the iron concentration in the molten zinc becomes 15% to 30% and the temperature of the steel sheet falls below 782 ° C., zinc-iron alloying proceeds. . The phase produced by this alloying is a Γ phase.
　亜鉛めっき鋼板のホットスタンプを行う場合、以下のような理由により、プレスを行うタイミングが重要である。もし、合金化反応の開始前又は開始直後の状態で亜鉛めっき鋼板のプレスを行うと、未合金の溶融亜鉛に起因して鋼の粒界脆化割れが起こり製品とならない。また、鋼の粒界脆化割れが起きなくても、溶融亜鉛が金型の内面に凝着するため、金型の手入れを頻繁に行わねばならなくなる。更に、製品の表面の亜鉛めっき量が不足して耐食性の低下を招くこととなり、部品の性能上の問題を招く。このため、亜鉛めっき鋼板のホットスタンプにおいては、中間冷却工程において合金化反応を終了させた後にプレスを行うことが望ましい。 When hot stamping galvanized steel sheets, the timing of pressing is important for the following reasons. If the galvanized steel sheet is pressed before or immediately after the start of the alloying reaction, grain boundary embrittlement cracking of the steel occurs due to unalloyed molten zinc, and the product is not produced. Even if grain boundary embrittlement cracking does not occur in the steel, the molten zinc adheres to the inner surface of the mold, so that the mold must be frequently maintained. In addition, the amount of galvanizing on the surface of the product is insufficient, which leads to a decrease in corrosion resistance, leading to problems in the performance of the parts. For this reason, in the hot stamping of a galvanized steel sheet, it is desirable to perform pressing after finishing the alloying reaction in the intermediate cooling step.
　しかしながら、亜鉛めっき鋼板は多種多様にわたり、めっきの種類、目付量、板厚、及びサイズなどは様々であるから、加熱工程及び中間冷却工程を適切に管理して適切なタイミングでプレスを開始することは容易ではない。すなわち、従来は、経験的に、加熱時間、加熱温度、中間冷却時間、及びプレスを開始する温度に基づいた管理を行っているが、合金化反応の終了を正確に見極めることは困難である。 However, since there are a wide variety of galvanized steel sheets and the types of plating, weight per unit area, sheet thickness, size, etc. are various, the heating process and the intermediate cooling process should be properly managed and pressing be started at an appropriate timing. Is not easy. That is, conventionally, management based on the heating time, the heating temperature, the intermediate cooling time, and the temperature at which the press is started is empirically performed, but it is difficult to accurately determine the end of the alloying reaction.
　Ｘ線回折により亜鉛めっき鋼板の表面を観察し、その結果に基づいて合金化反応の終了を検出することも考えられるが、このためには、大掛かりな装置が必要となり、設備費が高くなる。また、プレスを実施する程の高温状態での検出は困難である。また、目視による観察では、特に高温状態であるために個人差が大きく、安定した管理が行えないという問題がある。 It is conceivable to observe the surface of the galvanized steel sheet by X-ray diffraction and detect the end of the alloying reaction based on the result, but this requires a large-scale apparatus and increases the equipment cost. Moreover, it is difficult to detect in a high temperature state enough to perform pressing. In addition, the visual observation has a problem that individual management is large due to a high temperature condition, and stable management cannot be performed.
　なお、特許文献１には、亜鉛めっき鋼板を加熱炉において８００℃～９５０℃に加熱した後、急冷設備で５００℃～７３０℃に急冷し、次いでプレスを行う方法が開示されている。しかし、この方法は耐食性と耐疲労特性の向上を狙った特殊な技術であるうえ、急冷設備を必要とすることもあり、一般的な亜鉛めっき鋼板のホットスタンプに適用することはできない。 Patent Document 1 discloses a method in which a galvanized steel sheet is heated to 800 ° C. to 950 ° C. in a heating furnace, then rapidly cooled to 500 ° C. to 730 ° C. with a quenching equipment, and then pressed. However, this method is a special technique aiming at improving corrosion resistance and fatigue resistance, and also requires a quenching equipment, and cannot be applied to a general hot stamping of a galvanized steel sheet.
　また、合金Ｚｎめっき鋼板の製造の際のＦｅ－Ｚｎ系の合金反応の進行具合を分光放射率に基づいて観察する方法が特許文献２に記載されている。しかし、特許文献２に記載された方法で観察が行われる温度域は、ホットスタンプにおいてプレスが行われる温度と比較して著しく低い。このため、特許文献２に記載された方法で、ホットスタンプの中間冷却工程における亜鉛めっき鋼板の表面の状態を検出することはできない。 Further, Patent Document 2 describes a method of observing the progress of the Fe—Zn alloy reaction during the production of the alloy Zn-plated steel sheet based on the spectral emissivity. However, the temperature range in which observation is performed by the method described in Patent Document 2 is significantly lower than the temperature at which pressing is performed in a hot stamp. For this reason, the state of the surface of the galvanized steel sheet in the hot stamp intermediate cooling process cannot be detected by the method described in Patent Document 2.
特開２００７－１８２６０８号公報JP 2007-182608 A 特開平７－５５７３７号公報JP-A-7-55737
　本発明は、確実に溶融亜鉛を消失させた上でプレス及び焼入れを行うことができる亜鉛めっき鋼板のホットスタンプ方法を提供することを目的とする。 An object of the present invention is to provide a hot stamping method for a galvanized steel sheet, which can be pressed and quenched after the molten zinc is surely lost.
　本発明者らは、加熱後の冷却の際に、所定の温度域内で所定の観察波長の放射率測定器により亜鉛めっき鋼板の表面の放射率の変化を測定し、放射率の変化に基づいて合金化反応の開始、終了、即ち溶融亜鉛の消失を検出することができることを見出した。そして、本発明者らは、以下に示す発明の諸態様に相当した。 The inventors measured the change in the emissivity of the surface of the galvanized steel sheet with an emissivity measuring device having a predetermined observation wavelength within a predetermined temperature range during cooling after heating, and based on the change in emissivity. It has been found that the start and end of the alloying reaction, that is, the disappearance of molten zinc can be detected. The inventors corresponded to the following aspects of the invention.
　（１）
　亜鉛めっき鋼板を、亜鉛の沸点未満、かつオーステナイト変態温度以上の温度に加熱する工程と、
　次いで、前記亜鉛めっき鋼板を冷却する工程と、
　次いで、前記亜鉛めっき鋼板のプレス及び焼入れを行う工程と、
　を有し、
　前記亜鉛めっき鋼板を冷却する工程において、亜鉛の沸点未満、かつフェライト変態温度以上の温度域内で、前記亜鉛めっき鋼板の表面の放射率の変化を、観察波長が１．４μｍ以上の放射率測定器により測定し、
　前記プレス及び焼入れを、前記放射率の変化に基づいて合金化反応の終了を検出した後に開始することを特徴とする亜鉛めっき鋼板のホットスタンプ方法。 (1)
Heating the galvanized steel sheet to a temperature below the boiling point of zinc and above the austenite transformation temperature;
Then, cooling the galvanized steel sheet,
Next, a step of pressing and quenching the galvanized steel sheet,
Have
In the step of cooling the galvanized steel sheet, a change in the emissivity of the surface of the galvanized steel sheet within a temperature range below the boiling point of zinc and above the ferrite transformation temperature, an emissivity measuring instrument having an observation wavelength of 1.4 μm or more Measured by
A hot stamping method for a galvanized steel sheet, wherein the pressing and quenching are started after detecting the end of the alloying reaction based on the change in emissivity.
　（２）
　前記亜鉛めっき鋼板の表面の放射率を、連続して測定することを特徴とする（１）に記載の亜鉛めっき鋼板のホットスタンプ方法。 (2)
The hot stamping method for a galvanized steel sheet according to (1), wherein the emissivity of the surface of the galvanized steel sheet is continuously measured.
　（３）
　前記放射率測定器として、測定素子がＩｎＧａＡｓ素子又はサーモパイルのものを用いることを特徴とする（１）又は（２）に記載の亜鉛めっき鋼板のホットスタンプ方法。 (3)
The hot stamping method for a galvanized steel sheet according to (1) or (2), wherein the emissivity measuring instrument is an InGaAs element or a thermopile measuring element.
　（４）
　前記亜鉛めっき鋼板の表面の放射率の変化を測定する際に、
　前記放射率測定器により測定された放射率を移動平均処理で平滑化し、
　次いで、微分処理して放射率の変化速度を取得し、
　次いで、前記放射率の変化速度が負値から正値に変わる点を前記合金化反応の開始点と判定し、その後に正値から負値に変わる点を前記合金化反応の終了点と判定することを特徴とする（１）～（３）のいずれかに記載の亜鉛めっき鋼板のホットスタンプ方法。 (4)
When measuring the change in emissivity of the surface of the galvanized steel sheet,
The emissivity measured by the emissivity measuring device is smoothed by a moving average process,
Next, differential processing is performed to obtain the rate of change of emissivity,
Next, the point at which the rate of change of the emissivity changes from a negative value to a positive value is determined as the starting point of the alloying reaction, and the point after which the rate of change from the positive value to the negative value is determined as the end point of the alloying reaction. The hot stamping method for a galvanized steel sheet according to any one of (1) to (3).
　（５）
　前記放射率測定器として、観察波長が８μｍ～４０μｍのものを用いることを特徴とする（１）～（４）のいずれかに記載の亜鉛めっき鋼板のホットスタンプ方法。 (5)
The hot stamping method for a galvanized steel sheet according to any one of (1) to (4), wherein the emissivity measuring instrument has an observation wavelength of 8 μm to 40 μm.
　（６）
　（１）～（５）のいずれかに記載のホットプレス方法における、前記亜鉛めっき鋼板を加熱する工程と、前記亜鉛めっき鋼板を冷却する工程とを有するホットスタンプのオフライン試験装置に、（１）～（５）のいずれかに記載の放射率測定器を設置して前記放射率測定器による測定を実行し、前記放射率の変化に基づいて冷却開始から合金化反応の終了を検出するまでの合金化反応終了時間を調査しておき、実際のホットスタンプを実施する設備において、制御手段に前記合金化反応終了時間を記憶させ、これに従って前記合金化反応終了時間に達したことを前記制御手段が検出した後に、前記プレス及び焼入れを開始するホットスタンプを行うことを特徴とする亜鉛めっき鋼板のホットスタンプ方法。 (6)
In the hot press method according to any one of (1) to (5), an off-line test apparatus for hot stamping comprising the steps of heating the galvanized steel sheet and cooling the galvanized steel sheet. The emissivity measuring device according to any one of (5) to (5) is installed and the measurement by the emissivity measuring device is executed, and from the start of cooling to the end of the alloying reaction is detected based on the change in the emissivity. In the facility for carrying out the actual hot stamping, the alloying reaction end time is investigated, the control means stores the alloying reaction end time, and the control means determines that the alloying reaction end time has been reached accordingly. A hot stamping method for a galvanized steel sheet, wherein hot stamping for starting the pressing and quenching is performed after the detection.
　（７）
　ホットスタンプのオフライン試験装置にて、（１）～（５）のいずれかに記載のホットプレス方法における、前記亜鉛めっき鋼板を加熱する工程と、前記亜鉛めっき鋼板を冷却する工程と、を実行し、更に、前記亜鉛めっき鋼板を冷却する工程において、前記放射率測定器による測定を実行し、前記放射率の変化に基づいて冷却開始から合金化反応の終了を検出するまでの合金化反応終了時間を調査しておき、
　実際のホットスタンプを実施する設備の制御手段に前記合金化反応終了時間を記憶させ、
　前記設備において、
　前記亜鉛めっき鋼板と同じ組成の第２の亜鉛めっき鋼板を、前記亜鉛めっき鋼板の加熱時と実質的に同一の温度まで加熱する工程と、
　次いで、前記第２の亜鉛めっき鋼板を、前記亜鉛めっき鋼板の冷却時と実質的に同一の速度で冷却する工程と、
　次いで、前記第２の亜鉛めっき鋼板のプレス及び焼入れを行う工程と、
　を有し、
　前記第２の亜鉛めっき鋼板を冷却する工程において、冷却開始からの経過時間を測定し、
　前記経過時間が前記合金化反応終了時間に達したことを前記制御手段が検出した後に、前記プレス及び焼入れを開始することを特徴とする亜鉛めっき鋼板のホットスタンプ方法。 (7)
In the hot stamp offline test apparatus, the step of heating the galvanized steel sheet and the step of cooling the galvanized steel sheet in the hot press method according to any one of (1) to (5) are performed. Further, in the step of cooling the galvanized steel sheet, the measurement by the emissivity measuring device is executed, and the alloying reaction end time from the start of cooling to the end of the alloying reaction is detected based on the change in the emissivity. Investigate
The alloying reaction end time is stored in the control means of the facility that performs the actual hot stamping,
In the equipment,
Heating a second galvanized steel sheet having the same composition as the galvanized steel sheet to a temperature substantially the same as that when heating the galvanized steel sheet;
Next, the step of cooling the second galvanized steel sheet at substantially the same rate as when cooling the galvanized steel sheet,
Next, a step of pressing and quenching the second galvanized steel sheet,
Have
In the step of cooling the second galvanized steel sheet, the elapsed time from the start of cooling is measured,
A hot stamping method for a galvanized steel sheet, wherein the pressing and quenching are started after the control means detects that the elapsed time has reached the alloying reaction end time.
　本発明によれば、亜鉛めっき鋼板のめっきの種類、目付量、板厚、サイズなどに関係なく、合金化反応の終了を確実に把握することができる。従って、確実に溶融亜鉛を消失させた上でプレス及び焼入れを行うことができる。 According to the present invention, the end of the alloying reaction can be reliably grasped regardless of the type, basis weight, plate thickness, size, etc. of the galvanized steel plate. Therefore, pressing and quenching can be performed after the molten zinc is surely lost.
図１は、本発明の実施態様（１）～（５）に係る亜鉛めっき鋼板のホットスタンプ方法の実施に好適な設備を示すブロック図である。FIG. 1 is a block diagram showing equipment suitable for carrying out a hot stamping method for galvanized steel sheets according to embodiments (1) to (5) of the present invention. 図２は、熱電対により測定された温度の変化、及び放射率の温度換算により算出された温度の変化を示すグラフである。FIG. 2 is a graph showing a change in temperature measured by a thermocouple and a change in temperature calculated by temperature conversion of emissivity. 図３は、熱電対による温度測定値及び各種観察波長を用いた放射率測定器による放射率の温度換算表示値を示すグラフである。FIG. 3 is a graph showing temperature-measured values by a thermocouple and emissivity temperature-converted display values by an emissivity measuring device using various observation wavelengths. 図４は、図３のグラフ中の観察波長が８μｍ～１４μｍの場合について、縦軸を放射率の変化速度に置き換えたグラフである。FIG. 4 is a graph in which the vertical axis is replaced with the rate of change of emissivity when the observation wavelength in the graph of FIG. 3 is 8 μm to 14 μm. 図５は、本発明の実施態様（６）に係る亜鉛めっき鋼板のホットスタンプ方法の実施に好適な設備を示すブロック図である。FIG. 5 is a block diagram showing equipment suitable for carrying out the hot stamping method for a galvanized steel sheet according to the embodiment (6) of the present invention.
　以下、本発明の実施形態について、添付の図面を参照しながら詳細に説明する。図１は、本発明の実施形態に係る亜鉛めっき鋼板のホットスタンプ方法の実施に好適な設備を示すブロック図である。 Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing equipment suitable for carrying out a hot stamping method for a galvanized steel sheet according to an embodiment of the present invention.
　この設備には、亜鉛めっき鋼板Ｗを所定の温度に加熱する加熱装置１、加熱装置１から取り出された亜鉛めっき鋼板Ｗを放冷等により冷却する中間冷却部３、及び、中間冷却部３において冷却された亜鉛めっき鋼板Ｗのプレス及び焼入れを行うプレス焼入れ装置２が設けられている。更に、中間冷却部３にある亜鉛めっき鋼板Ｗの表面の放射率を測定する放射率測定器４が設けられている。 The equipment includes a heating device 1 for heating the galvanized steel sheet W to a predetermined temperature, an intermediate cooling unit 3 for cooling the galvanized steel plate W taken out from the heating device 1 by cooling, and an intermediate cooling unit 3. A press hardening apparatus 2 for pressing and quenching the cooled galvanized steel sheet W is provided. Furthermore, an emissivity measuring device 4 for measuring the emissivity of the surface of the galvanized steel sheet W in the intermediate cooling unit 3 is provided.
　亜鉛めっき鋼板Ｗは、溶融亜鉛めっき鋼板及び電気亜鉛めっき鋼板のいずれであってもよい。なお、目付量が４５ｇ／ｍ２の冷間プレス用の合金化溶融亜鉛めっき鋼板と同等以上の耐食性をホットスタンプ部品で得るには、溶融亜鉛めっき鋼板では目付量を５０ｇ／ｍ２以上、合金化溶融亜鉛めっき鋼板では６０ｇ／ｍ２以上、電気亜鉛めっき鋼板では５０ｇ／ｍ２以上、合金化電気亜鉛めっき鋼板では６０ｇ／ｍ２以上が必要である。 The galvanized steel sheet W may be either a hot dip galvanized steel sheet or an electrogalvanized steel sheet. In order to obtain hot stamping parts with corrosion resistance equivalent to or higher than that of an alloyed hot-dip galvanized steel sheet for cold pressing with a basis weight of 45 g / m 2 , the weight per unit area of hot-dip galvanized steel sheet is 50 g / m 2 the galvannealed steel sheet 60 g / m 2 or more, the electro-galvanized steel sheet 50 g / m 2 or more, the alloying galvanized steel sheet is required 60 g / m 2 or more.
　ホットスタンプの前段の加熱装置１としては、通電加熱、加熱炉、近赤外線加熱、遠赤外線加熱、及び誘導加熱などの各種の装置を採用することができる。自動車用部品をホットスタンプするような場合には、通電加熱装置を用いることが好ましい。これは、通電加熱装置はコンパクトであり、また、通電加熱によれば、速い加熱速度が得られるために生産性を向上することができ、加熱温度を制御しやすく、亜鉛めっき鋼板を均一に加熱することができるからである。また、加熱装置１における加熱最高温度はＡｃ３点以上、亜鉛の沸点未満であり、実用上は８００℃～９００℃の範囲である。亜鉛めっき鋼板Ｗの加熱速度は１０℃／秒以上、２００℃／秒以下が実用的であり、生産性を高める観点からは２０℃／秒～２００℃／秒の範囲が好ましい。 As the heating device 1 before the hot stamp, various devices such as energization heating, a heating furnace, near infrared heating, far infrared heating, and induction heating can be employed. When hot stamping automotive parts, it is preferable to use an electric heating device. This is because the current heating device is compact, and according to the current heating, a high heating rate can be obtained, so that the productivity can be improved, the heating temperature is easily controlled, and the galvanized steel sheet is heated uniformly. Because it can be done. The maximum heating temperature in the heating device 1 is not less than Ac3 and less than the boiling point of zinc, and is practically in the range of 800 ° C to 900 ° C. The heating rate of the galvanized steel sheet W is practically 10 ° C./second or more and 200 ° C./second or less, and is preferably in the range of 20 ° C./second to 200 ° C./second from the viewpoint of improving productivity.
　前述したように、この温度域（Ａｃ３点以上、亜鉛の沸点未満）においては溶融亜鉛への鉄の液相拡散によって鉄及び亜鉛の合金化反応が進行する。ここで、加熱装置１において加熱を行い、その後に中間冷却部３において冷却を行う場合の溶融亜鉛めっき鋼板の温度変化について説明する。溶融亜鉛めっき鋼板の温度は、熱電対により測定され、また、放射率測定器によって測定された放射率の温度換算により算出されるものとする。以下、熱電対により測定された温度を「熱電対による温度測定値」といい、放射率測定器によって測定された放射率の温度換算により算出された値を「放射率の温度換算表示値」ということがある。放射率の温度換算表示値は、実質的に放射率の値及びその変化と同等である。図２に、熱電対による温度測定値及び放射率の温度換算表示値を示す。図２中の実線は加熱開始からの熱電対による温度測定値の変化を示し、一点鎖線は加熱開始からの観察波長が１．４μｍ～１．８μｍの放射率測定器を用いた場合の放射率の温度換算表示値の変化を示す。この例では、亜鉛めっき鋼板の温度が最高温度（約８８０℃、加熱開始から約１０秒時点）に到達した後から１７秒間程度経過した時点で合金化反応が開始し、最高温度に到達した後から２５秒間程度経過した時点で合金化反応が終了している。そして、図２に示すように、放射率の温度換算表示値には、合金化の開始点及び終了点に明確な変化が現れており、放射率測定器の観察波長の変化と合金化の開始点及び終了点との間には相関があるといえる。一方、熱電対による温度測定値には、合金化反応の影響は全く現れず、この温度変化から合金化反応の終了を把握することは不可能である。 As described above, in this temperature range (3 points or more of Ac and less than the boiling point of zinc), the alloying reaction of iron and zinc proceeds by liquid phase diffusion of iron into molten zinc. Here, the temperature change of the hot-dip galvanized steel sheet when heating is performed in the heating device 1 and then cooling is performed in the intermediate cooling unit 3 will be described. The temperature of the hot-dip galvanized steel sheet is measured by a thermocouple, and is calculated by converting the emissivity measured by the emissivity measuring device into a temperature. Hereinafter, the temperature measured by the thermocouple is referred to as the “temperature measurement value by the thermocouple”, and the value calculated by the temperature conversion of the emissivity measured by the emissivity measuring instrument is referred to as the “emissivity temperature conversion display value”. Sometimes. The temperature converted display value of the emissivity is substantially equivalent to the emissivity value and its change. In FIG. 2, the temperature measurement value by a thermocouple and the temperature conversion display value of emissivity are shown. The solid line in Fig. 2 shows the change in the temperature measurement value due to the thermocouple from the start of heating, and the alternate long and short dash line indicates the emissivity when using an emissivity measuring instrument with an observation wavelength of 1.4 µm to 1.8 µm from the start of heating. The change of the temperature conversion display value of is shown. In this example, after the temperature of the galvanized steel sheet reaches the maximum temperature (about 880 ° C., about 10 seconds from the start of heating) after about 17 seconds, the alloying reaction starts, and after reaching the maximum temperature The alloying reaction is completed when about 25 seconds have passed. As shown in FIG. 2, in the temperature converted display value of emissivity, a clear change appears at the start point and end point of alloying, and the change in the observation wavelength of the emissivity measuring device and the start of alloying are observed. It can be said that there is a correlation between the point and the end point. On the other hand, the influence of the alloying reaction does not appear at all in the temperature measurement value by the thermocouple, and it is impossible to grasp the end of the alloying reaction from this temperature change.
　また、上述のように、加熱装置１における加熱速度は、生産性を高める観点から比較的高速な２０℃／秒～２００℃／秒の範囲が好ましい。そして、合金化反応の終了を把握する温度域は、めっき層の亜鉛の沸点未満、鋼板のフェライト変態温度以上とする。合金化反応の終了を把握する温度域をめっき層の亜鉛の沸点未満とするのは、沸点以上に加熱を行うと、鋼板表面から亜鉛が蒸発して亜鉛が消失し亜鉛めっき鋼板ではなくなるからである。この温度域を鋼板のフェライト変態温度以上とするのは、プレス焼入れ装置２での焼入れによって安定してマルテンサイト組織を得るためである。焼入れによって安定してマルテンサイト組織を得るためには、焼入れをフェライト変態温度以上で行う必要があり、フェライト変態温度未満で合金化反応の終了を把握しても、焼入れによって安定してマルテンサイト組織を得ることはできない。図２の例では、亜鉛の沸点未満の温度である約８８０℃まで加熱し、その後の中間冷却工程での合金化反応の終了温度は約７００℃となっていて、一方、フェライト変態は約６５０℃で起きている。 Further, as described above, the heating rate in the heating device 1 is preferably in the range of 20 ° C./second to 200 ° C./second, which is relatively fast, from the viewpoint of improving productivity. And the temperature range which grasps | ascertains completion | finish of alloying reaction shall be below the boiling point of zinc of a plating layer, and more than the ferrite transformation temperature of a steel plate. The temperature range for grasping the end of the alloying reaction is set to be less than the boiling point of zinc in the plating layer because heating to a temperature higher than the boiling point causes the zinc to evaporate from the steel sheet surface and disappear, resulting in no longer a galvanized steel sheet. is there. The reason why the temperature range is set to be equal to or higher than the ferrite transformation temperature of the steel sheet is to obtain a martensite structure stably by quenching in the press quenching apparatus 2. In order to obtain a stable martensite structure by quenching, it is necessary to perform the quenching at a temperature higher than the ferrite transformation temperature. Even if the completion of the alloying reaction is grasped at a temperature lower than the ferrite transformation temperature, the martensite structure is stably obtained by quenching. Can't get. In the example of FIG. 2, heating is performed to about 880 ° C., which is a temperature below the boiling point of zinc, and the end temperature of the alloying reaction in the subsequent intermediate cooling step is about 700 ° C., while the ferrite transformation is about 650 ° C. Waking up at ℃.
　亜鉛の沸点は、溶融亜鉛めっき鋼板、合金化溶融亜鉛めっき鋼板、電気亜鉛めっき鋼板、合金化電気亜鉛めっき鋼板では、めっき層に含まれる他の金属元素の量によって多少変化するものの、９０８℃程度である。また、フェライト変態温度は、鋼板のＣ量がホットスタンプに適する場合の０．１８質量％～０．２５質量％の範囲では、鋼板の他の化学成分並びに加熱装置１における加熱速度及び加熱温度等によって多少変化するものの、６５０℃程度である。 The boiling point of zinc varies slightly depending on the amount of other metal elements contained in the plating layer in the hot dip galvanized steel sheet, alloyed hot dip galvanized steel sheet, electrogalvanized steel sheet, and alloyed electrogalvanized steel sheet, but about 908 ° C It is. Further, the ferrite transformation temperature is in the range of 0.18 mass% to 0.25 mass% when the C amount of the steel sheet is suitable for hot stamping, and other chemical components of the steel sheet, the heating rate and the heating temperature in the heating apparatus 1, etc. However, it is about 650 ° C.
　亜鉛めっき鋼板の温度測定は、一般的に熱電対又は放射温度計を用いて行われるが、放射温度計を用いた温度測定では、熱電対を用いた場合として比較して約２０℃程度の差を生じることがある。 The temperature measurement of a galvanized steel sheet is generally performed using a thermocouple or a radiation thermometer. However, in the temperature measurement using a radiation thermometer, the difference is about 20 ° C. compared to the case where a thermocouple is used. May occur.
　そこで、本願発明者は、放射率測定器の観察波長、及びその波長における放射率の温度換算表示値の変化に着目した。そして、本実施形態では、加熱装置１において、例えば８００℃～９００℃まで加熱した亜鉛めっき鋼板Ｗを中間冷却部３に取り出し、加熱装置１において加熱された亜鉛めっき鋼板Ｗの表面の放射率を、観察波長が１．４μｍ以上の長波長の放射率測定器４、より好ましくは観察波長が８μｍ～４０μｍの放射率測定器４により測定する。合金化反応の進行に伴って、亜鉛めっき鋼板Ｗの表面状態が液体から固体へと変化し、物性が変化する。そして、これらの変化に付随して赤外線量が変化する。本実施形態は、このような赤外線量の変化を、放射率又は放射率の温度換算表示値の変化として前述の長波長の観察波長で連続的に検出することにより、合金化反応の開始、終了及び溶融亜鉛の消失を把握しようとするものである。 Therefore, the inventor of the present application focused on the observation wavelength of the emissivity measuring device and the change in the temperature converted display value of the emissivity at that wavelength. In the present embodiment, the galvanized steel sheet W heated to, for example, 800 ° C. to 900 ° C. in the heating device 1 is taken out to the intermediate cooling unit 3, and the emissivity of the surface of the galvanized steel sheet W heated in the heating device 1 is determined. The measurement is performed with the emissivity measuring instrument 4 having a long wavelength of 1.4 μm or more, more preferably the emissivity measuring instrument 4 having an observation wavelength of 8 μm to 40 μm. As the alloying reaction proceeds, the surface state of the galvanized steel sheet W changes from liquid to solid, and the physical properties change. And the amount of infrared rays changes accompanying these changes. In this embodiment, the start and end of the alloying reaction are detected by continuously detecting such a change in the amount of infrared rays at the aforementioned long wavelength observation wavelength as a change in emissivity or a temperature-converted display value of emissivity. It is intended to grasp the disappearance of molten zinc.
　本実施形態で用いる放射率測定器４には、測定素子がＩｎＧａＡｓ素子又はサーモパイルであるものが適していて、特に放射率の変化を大きく捉えることができるサーモパイルが好ましい。また、測定素子がサーモパイルである場合、観察波長の上限は実用上４０μｍとなる。サーモパイルは複数の熱電対を直列又は並列に接続したもので、熱エネルギーを電気エネルギーに変換する機能を有する変換器であり、熱電推ともよばれる。多数の小型の熱電対の温接点を集中させることにより、熱放射を精度よく測定することができる。 For the emissivity measuring instrument 4 used in the present embodiment, a measuring element that is an InGaAs element or a thermopile is suitable, and a thermopile that can capture a large change in emissivity is particularly preferable. When the measuring element is a thermopile, the upper limit of the observation wavelength is practically 40 μm. A thermopile is a converter in which a plurality of thermocouples are connected in series or in parallel, and is a converter having a function of converting heat energy into electric energy, and is also referred to as thermoelectric estimation. By concentrating the hot junctions of many small thermocouples, it is possible to accurately measure thermal radiation.
　このように、本実施形態では、合金化反応の開始及び終了を検知するために、観察波長が１．４μｍ以上の長波長の放射率測定器４を用いる。図３に、熱電対による温度測定値及び各種観察波長を用いた放射率測定器による放射率の温度換算表示値を示す。図３中の破線は観察波長が０．８μｍ～１．１μｍの短波長の放射率測定器を用いた場合の加熱開始からの放射率の温度換算表示値の変化を示し、一点鎖線は観察波長が１．４μｍ～１．８μｍの放射率測定器を用いた場合の加熱開始からの放射率の温度換算表示値の変化を示し、二点鎖線は観察波長が８μｍ～１４μｍの放射率測定器を用いた場合の加熱開始からの放射率の温度換算表示値の変化を示す。図３に示すように、観察波長が０．８μｍ～１．１μｍの短波長の放射率測定器を用いた場合（破線）の変化は小さく、合金化反応の開始点及び終了点を明確に捉えることができない。これに対して、観察波長が１．４μｍ～１．８μｍの放射率測定器を用いた場合（一点鎖線）には、合金化反応の開始点及び終了点における変化が大きく、これらを明確に捉えることができる。また、観察波長が８μｍ～１４μｍの放射率測定器を用いた場合（二点鎖線）には、合金化反応の開始点及び終了点における変化が更に大きく、これらをより明確に捉えることができる。 Thus, in this embodiment, in order to detect the start and end of the alloying reaction, a long wavelength emissivity measuring instrument 4 with an observation wavelength of 1.4 μm or more is used. In FIG. 3, the temperature conversion value by the emissivity by the emissivity measuring device using the temperature measurement value by a thermocouple and various observation wavelengths is shown. The broken line in FIG. 3 shows the change in the temperature-converted display value of the emissivity from the start of heating when using a short-wavelength emissometer with an observation wavelength of 0.8 μm to 1.1 μm. Shows the change in the temperature-converted display value of the emissivity from the start of heating when using an emissivity measuring instrument of 1.4 μm to 1.8 μm, and the two-dot chain line shows the emissivity measuring instrument with an observation wavelength of 8 μm to 14 μm. The change of the temperature conversion display value of the emissivity from the heating start at the time of using is shown. As shown in FIG. 3, when using an emissivity measuring instrument with a short wavelength of 0.8 μm to 1.1 μm (dashed line), the change is small and the starting and ending points of the alloying reaction are clearly captured. I can't. On the other hand, when using an emissivity measuring instrument with an observation wavelength of 1.4 μm to 1.8 μm (dashed line), changes at the start and end points of the alloying reaction are large, and these are clearly captured. be able to. In addition, when an emissivity measuring instrument having an observation wavelength of 8 μm to 14 μm is used (two-dot chain line), the change at the starting point and the ending point of the alloying reaction is further large, and these can be captured more clearly.
　また、図４に、図３のグラフ中の観察波長が８μｍ～１４μｍの場合について、縦軸を放射率の変化速度に置き換えたグラフを示す。図４に示すように、放射率の変化速度（実線）は、合金化反応の開始点まではほぼ一定であり、合金化反応の開始点において増加し、その後に減少し、合金化反応の終了点からは再びほぼ一定となる。つまり、放射率の変化速度も合金化反応の開始点及び終了点において大きく変化する。従って、放射率の変化速度が一定値から増加に転ずる点を合金化反応の開始点、その後に一定値に転ずる点を合金化反応の終了点と判定するようにすれば、より明確に合金化反応の終了点を見極めることができる。この判定は、放射率の測定値を移動平均処理などで平滑化した値を微分処理すればより明確に把握できる。特に中間冷却部３での中間冷却工程で、負値から正値に変化する点を合金化開始点、その後に正値から負値に変化する点を合金化終了点とすれば、より明確に合金化反応の終了点を見極めることができる。 FIG. 4 shows a graph in which the vertical axis is replaced with the rate of change of emissivity when the observation wavelength in the graph of FIG. 3 is 8 μm to 14 μm. As shown in FIG. 4, the rate of change of emissivity (solid line) is substantially constant up to the starting point of the alloying reaction, increases at the starting point of the alloying reaction, decreases thereafter, and ends the alloying reaction. From the point it becomes almost constant again. That is, the rate of change of emissivity also varies greatly at the start and end points of the alloying reaction. Therefore, if the rate at which the rate of change in emissivity starts to increase from a certain value is judged as the starting point of the alloying reaction, and the point after which it changes to a constant value is judged as the end point of the alloying reaction, alloying becomes clearer. The end point of the reaction can be determined. This determination can be grasped more clearly by differentiating the value obtained by smoothing the measured emissivity value by moving average processing or the like. In particular, in the intermediate cooling step in the intermediate cooling section 3, if the point at which the negative value changes to the positive value is the alloying start point, and the point after which the positive value changes to the negative value is the alloying end point, it becomes clearer. The end point of the alloying reaction can be determined.
　なお、移動平均処理は、時系列データを平滑化する手法であり、例えば、単純移動平均処理を行えばよい。単純移動平均処理とは、最新のデータから直近のｎ個のデータの重みを付けない単純な平均値を求める処理である。時間が進んで最新のデータを計測すると、最新のデータを加えると共に最も古いデータを除いて改めてｎ個の平均値を求める。単純移動平均処理では、以後、これを繰り返していく。図４のグラフの作成でも単純移動平均処理を行っており、この際には、０．１秒毎に放射率測定器からのデータを採取し、移動平均処理のデータ数は１０個とした。なお、移動平均処理として、単純移動平均処理以外の移動平均処理を用いても構わない。 Note that the moving average process is a technique for smoothing time-series data. For example, a simple moving average process may be performed. The simple moving average process is a process for obtaining a simple average value that does not weight the latest n data from the latest data. When time advances and the latest data is measured, the latest data is added and n average values are obtained again except for the oldest data. In the simple moving average process, this is repeated thereafter. In the creation of the graph of FIG. 4, the simple moving average processing is performed. At this time, data from the emissivity measuring device is sampled every 0.1 second, and the number of data of the moving average processing is 10. As the moving average process, a moving average process other than the simple moving average process may be used.
　本実施形態では、このようにして合金化反応の終了を検出した後に亜鉛めっき鋼板Ｗをプレス焼入れ装置２に送り込み、フェライト変態温度以上の温度となっている間にプレス及び焼入れを開始する。つまり、合金化反応の終了を把握し、確実に溶融亜鉛を消失させた上でプレス及び焼入れを開始する。 In this embodiment, after the end of the alloying reaction is detected in this way, the galvanized steel sheet W is fed into the press hardening apparatus 2 and the press and quenching are started while the temperature is equal to or higher than the ferrite transformation temperature. That is, the completion of the alloying reaction is grasped, and after the molten zinc is surely lost, pressing and quenching are started.
　このため、本実施形態によれば、亜鉛めっき鋼板Ｗのめっき種類、目付量、板厚、サイズなどに関係なく、合金化反応が終了した後にプレス及び焼入れを開始することができる。従って、未合金の溶融亜鉛に起因する鋼の粒界脆化割れを防止することができる。また、溶融亜鉛のプレス焼入れ装置２の金型の内面への凝着、及び亜鉛めっき量の不足による耐食性の低下を防止することもできる。特に、放射率変化速度が負値から正値に変わる点を合金化反応の開始点、その後に正値から負値に変わる点を合金化反応の終了点と判定するようにすれば、より的確な判断が可能となる。 For this reason, according to the present embodiment, the press and quenching can be started after the alloying reaction is completed regardless of the plating type, basis weight, plate thickness, size, etc. of the galvanized steel sheet W. Therefore, grain boundary embrittlement cracking of steel due to unalloyed molten zinc can be prevented. Moreover, the adhesion of the molten zinc to the inner surface of the mold of the press quenching apparatus 2 and the deterioration of the corrosion resistance due to the insufficient amount of galvanizing can be prevented. In particular, if the rate at which the rate of change in emissivity changes from a negative value to a positive value is determined as the starting point of the alloying reaction, and the point after which the rate of change from the positive value to the negative value is determined as the end point of the alloying reaction, it is more appropriate. Judgment is possible.
　なお、図１に示すように、放射率測定器４の測定値を演算制御装置５に入力し、演算制御装置５がプレス焼入れ装置２の動作を制御してもよい。 Note that, as shown in FIG. 1, the measurement value of the emissivity measuring device 4 may be input to the calculation control device 5, and the calculation control device 5 may control the operation of the press hardening device 2.
　また本発明では、設備的、スペース的あるいはコスト的に、ホットスタンプを実施する設備に放射率測定器４を設置できない場合、例えばオフライン試験装置に放射率測定器４を取り付け、このオフライン試験装置にて前述と同様の方法で合金化反応終了時間を調査しておき、図５に示すように実際のホットスタンプを実施する設備の演算制御装置５にこの合金化反応終了時間を記憶させ、冷却時に冷却開始からの経過時間を測定し、経過時間が合金化反応終了時間に達したことを演算制御装置５が検出した後に、プレス及び焼入れを開始してもよい。この方法によれば、放射率測定器４による実測定なしでも、確実に溶融亜鉛を消失させた上でホットスタンプを行うことができる。なお、この方法を行う場合、オフライン試験装置での加熱温度及び加熱後の冷却速度は、実際のホットスタンプを実施する設備におけるものと同一とする。但し、実際の設備での加熱温度及び冷却速度を、オフライン試験装置でのものと厳密に同一に制御せずとも、実質的に同一のものに制御すれば、多少のばらつきがあっても所望の効果が得られる。例えば、実際の設備での加熱温度をオフライン試験装置での加熱温度の±１０℃の範囲内に収め、実際の設備での冷却速度をオフライン試験装置での冷却速度の±２℃／秒の範囲内に収めれば、所望の効果を得ることができる。 Further, in the present invention, when the emissivity measuring instrument 4 cannot be installed in equipment for performing hot stamping in terms of equipment, space or cost, for example, the emissivity measuring instrument 4 is attached to an off-line test apparatus, and this off-line test apparatus is installed. Then, the alloying reaction end time is investigated in the same manner as described above, and the alloying reaction end time is stored in the arithmetic control unit 5 of the facility that performs the actual hot stamping as shown in FIG. The elapsed time from the start of cooling is measured, and after the arithmetic and control unit 5 detects that the elapsed time has reached the alloying reaction end time, pressing and quenching may be started. According to this method, it is possible to perform hot stamping without losing molten zinc even without actual measurement by the emissivity measuring device 4. When performing this method, the heating temperature and the cooling rate after heating in the off-line test apparatus are the same as those in the facility that performs the actual hot stamping. However, if the heating temperature and cooling rate in the actual equipment are not controlled exactly the same as those in the off-line test apparatus, but are controlled to be substantially the same, the desired temperature can be obtained even if there is some variation. An effect is obtained. For example, the heating temperature in the actual equipment is kept within the range of ± 10 ° C of the heating temperature in the offline test apparatus, and the cooling rate in the actual equipment is in the range of ± 2 ° C / second of the cooling speed in the offline test apparatus. If it fits in, the desired effect can be acquired.
　なお、上記実施形態は、何れも本発明を実施するにあたっての具体化の例を示したものに過ぎず、これらによって本発明の技術的範囲が限定的に解釈されてはならないものである。すなわち、本発明はその技術思想、又はその主要な特徴から逸脱することなく、様々な形で実施することができる。 It should be noted that each of the above-described embodiments is merely a specific example for carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.
　本発明は、例えば、車体等に用いられる亜鉛めっき鋼板の関連産業において利用することができる。 The present invention can be used, for example, in related industries of galvanized steel sheets used for vehicle bodies and the like.

Claims (7)

  1. 　亜鉛めっき鋼板を、亜鉛の沸点未満、かつオーステナイト変態温度以上の温度に加熱する工程と、
    　次いで、前記亜鉛めっき鋼板を冷却する工程と、
    　次いで、前記亜鉛めっき鋼板のプレス及び焼入れを行う工程と、
    　を有し、
    　前記亜鉛めっき鋼板を冷却する工程において、亜鉛の沸点未満、かつフェライト変態温度以上の温度域内で、前記亜鉛めっき鋼板の表面の放射率の変化を、観察波長が１．４μｍ以上の放射率測定器により測定し、
    　前記プレス及び焼入れを、前記放射率の変化に基づいて合金化反応の終了を検出した後に開始することを特徴とする亜鉛めっき鋼板のホットスタンプ方法。     Heating the galvanized steel sheet to a temperature below the boiling point of zinc and above the austenite transformation temperature;
    Then, cooling the galvanized steel sheet,
    Next, a step of pressing and quenching the galvanized steel sheet,
    Have
    In the step of cooling the galvanized steel sheet, a change in the emissivity of the surface of the galvanized steel sheet within a temperature range below the boiling point of zinc and above the ferrite transformation temperature, an emissivity measuring instrument having an observation wavelength of 1.4 μm or more Measured by
    A hot stamping method for a galvanized steel sheet, wherein the pressing and quenching are started after detecting the end of the alloying reaction based on the change in emissivity.
  2. 　前記亜鉛めっき鋼板の表面の放射率を、連続して測定することを特徴とする請求項１に記載の亜鉛めっき鋼板のホットスタンプ方法。 The method of hot stamping a galvanized steel sheet according to claim 1, wherein the emissivity of the surface of the galvanized steel sheet is continuously measured.
  3. 　前記放射率測定器として、測定素子がＩｎＧａＡｓ素子又はサーモパイルのものを用いることを特徴とする請求項１又は２に記載の亜鉛めっき鋼板のホットスタンプ方法。 3. The hot stamping method for a galvanized steel sheet according to claim 1, wherein the emissivity measuring instrument is an InGaAs element or a thermopile measuring element.
  4. 　前記亜鉛めっき鋼板の表面の放射率の変化を測定する際に、
    　前記放射率測定器により測定された放射率を移動平均処理で平滑化し、
    　次いで、微分処理して放射率の変化速度を取得し、
    　次いで、前記放射率の変化速度が負値から正値に変わる点を前記合金化反応の開始点と判定し、その後に正値から負値に変わる点を前記合金化反応の終了点と判定することを特徴とする請求項１乃至３のいずれか１項に記載の亜鉛めっき鋼板のホットスタンプ方法。     When measuring the change in emissivity of the surface of the galvanized steel sheet,
    The emissivity measured by the emissivity measuring device is smoothed by a moving average process,
    Next, differential processing is performed to obtain the rate of change of emissivity,
    Next, the point at which the rate of change of the emissivity changes from a negative value to a positive value is determined as the starting point of the alloying reaction, and the point after which the rate of change from the positive value to the negative value is determined as the end point of the alloying reaction. The hot stamping method for a galvanized steel sheet according to any one of claims 1 to 3.
  5. 　前記放射率測定器として、観察波長が８μｍ～４０μｍのものを用いることを特徴とする請求項１乃至４のいずれか１項に記載の亜鉛めっき鋼板のホットスタンプ方法。 5. The hot stamping method for a galvanized steel sheet according to claim 1, wherein the emissivity measuring instrument has an observation wavelength of 8 μm to 40 μm.
  6. 　請求項１乃至５のいずれか１項に記載のホットプレス方法における、前記亜鉛めっき鋼板を加熱する工程と、前記亜鉛めっき鋼板を冷却する工程とを有するホットスタンプのオフライン試験装置に、請求項１乃至５のいずれか１項に記載の放射率測定器を設置して前記放射率測定器による測定を実行し、前記放射率の変化に基づいて冷却開始から合金化反応の終了を検出するまでの合金化反応終了時間を調査しておき、実際のホットスタンプを実施する設備において、制御手段に前記合金化反応終了時間を記憶させ、これに従って前記合金化反応終了時間に達したことを前記制御手段が検出した後に、前記プレス及び焼入れを開始するホットスタンプを行うことを特徴とする亜鉛めっき鋼板のホットスタンプ方法。 In the hot press method of any one of Claims 1 thru | or 5, The offline test apparatus of the hot stamp which has the process of heating the said galvanized steel plate, and the process of cooling the said galvanized steel plate. From the start of cooling until the end of the alloying reaction is detected based on the change in the emissivity, the emissivity measuring device according to any one of 1 to 5 is installed and measurement is performed by the emissivity measuring device. In the facility for carrying out the actual hot stamping, the alloying reaction end time is investigated, the control means stores the alloying reaction end time, and the control means determines that the alloying reaction end time has been reached accordingly. A hot stamping method for a galvanized steel sheet, wherein hot stamping for starting the pressing and quenching is performed after the detection.
  7. 　ホットスタンプのオフライン試験装置にて、請求項１乃至５のいずれか１項に記載のホットプレス方法における、前記亜鉛めっき鋼板を加熱する工程と、前記亜鉛めっき鋼板を冷却する工程と、を実行し、更に、前記亜鉛めっき鋼板を冷却する工程において、前記放射率測定器による測定を実行し、前記放射率の変化に基づいて冷却開始から合金化反応の終了を検出するまでの合金化反応終了時間を調査しておき、
    　実際のホットスタンプを実施する設備の制御手段に前記合金化反応終了時間を記憶させ、
    　前記設備において、
    　前記亜鉛めっき鋼板と同じ組成の第２の亜鉛めっき鋼板を、前記亜鉛めっき鋼板の加熱時と実質的に同一の温度まで加熱する工程と、
    　次いで、前記第２の亜鉛めっき鋼板を、前記亜鉛めっき鋼板の冷却時と実質的に同一の速度で冷却する工程と、
    　次いで、前記第２の亜鉛めっき鋼板のプレス及び焼入れを行う工程と、
    　を有し、
    　前記第２の亜鉛めっき鋼板を冷却する工程において、冷却開始からの経過時間を測定し、
    　前記経過時間が前記合金化反応終了時間に達したことを前記制御手段が検出した後に、前記プレス及び焼入れを開始することを特徴とする亜鉛めっき鋼板のホットスタンプ方法。     In the hot stamp offline test apparatus, the step of heating the galvanized steel sheet and the step of cooling the galvanized steel sheet in the hot press method according to any one of claims 1 to 5 are performed. Further, in the step of cooling the galvanized steel sheet, the measurement by the emissivity measuring device is executed, and the alloying reaction end time from the start of cooling to the end of the alloying reaction is detected based on the change in the emissivity. Investigate
    The alloying reaction end time is stored in the control means of the facility that performs the actual hot stamping,
    In the equipment,
    Heating a second galvanized steel sheet having the same composition as the galvanized steel sheet to a temperature substantially the same as that when heating the galvanized steel sheet;
    Next, the step of cooling the second galvanized steel sheet at substantially the same rate as when cooling the galvanized steel sheet,
    Next, a step of pressing and quenching the second galvanized steel sheet,
    Have
    In the step of cooling the second galvanized steel sheet, the elapsed time from the start of cooling is measured,
    A hot stamping method for a galvanized steel sheet, wherein the pressing and quenching are started after the control means detects that the elapsed time has reached the alloying reaction end time.
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JP2020509179A (en) * 2016-12-19 2020-03-26 アルセロールミタル Method for producing hot-pressed aluminum-plated steel parts
US11401577B2 (en) 2016-12-19 2022-08-02 Arcelormittal Manufacturing process of hot press formed aluminized steel parts
JP7127027B2 (en) 2016-12-19 2022-08-29 アルセロールミタル Method for producing hot-pressed aluminized steel parts

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